Method oe producing punchings



I. 1. FRANK. 7 METHOD OF PRODUCING PUNCHINGS. APPLICATION FILED OCT. 26, 1918.

1,334, 1 49. Patented Mar. 16, 1920.

Inventor": John J. Frank,

has

His aqttor-neg JOHN J. FR.ANK, OF

IITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

METHOD OF PRODUCING PUNCHINGS.

and useful Improvements in Methods of Producing Punchings, of which the following is a specification.

My invention relates to a method of producing L-shaped punchings, such as the laminations used in the construction of cores for electrical apparatus. w In the manufacture of L-shaped punchings of a given size, it has generally been the practice to strike these punchings from a sheet of metal stock that is but slightly wider than the hypotenuse or distance across the tips of the legs of the-L-punching to be 7 the legs having such proportions that one L will nest in the next, the bend or knee of the Us lying along substantially a straight line to one slde of the center line of the sheet of stock. Even with this nesting of the L-punchings a considerable percentage of the stock went into the refuse because all along the edge of the stock there were substantially triangular pieces to be sheared off to give the ends of the legs of the L- punching their desired shape, which pieces produced;

were generally connected by a marginal strip.

It is the object, then of my invention, to reduce this waste by at least half and in some instance where the triangular pieces on the two sides ofthe stock are of different size a greater saving may be effected.

In order to accomplish this object I propose to usev a sheet of stock a little less than twice the normal width, and to strike a second lot of Us from the other side of the strip of sheet metal stock in such a manner that the homologous leg of the 'Ls from each side of the strip have their squared ends abutting, thereby eliminating entirely the waste material along one edge.

In order that my invention and the method of practising the same may be more fully comprehended, reference should be had to the following detailed description taken in connection with the accompanying drawing in which Figure 1 shows a plan view of a piece of metal stock having Ls punched from it in accordance with the method which I have invented. Fig. 2 is a similar view illustrating a modified manner of practisthat along t ofa compound die,

Specification of Letters Patent. Patented Mar. 16, 1920- Application filed October 26, 1918. Serial No. 259,881. 7

ing this invention. Fig. 3 is a plan view showing a piece of stock when. punched in accordance with this modification, and Figs. 4 and 5 illustrate respective conventional forms of punch press and punch suitable for use in the practice ofthis invention.

Referring now to Fig. 1 of the drawings, A denotes a piece of metal stock whose width is almost twice the-distance b which would be the width of stock required were it desired to stamp single successive Ls as 1, 2, 3 etc. out of a strip of stock.

If the stri were of the width b, it is seen lie upper edge of the strip the triangles t would be waste, while on the lower'edge the trianglesu would be waste.

Of the two triangles, it is seen that the triangle 25 is the larger since the triangle u is somewhat reduced because it is desired to have the longer leg of the L-punching formed with a diagonally cut corner as shown. .As a consequence the triangles t comprise the largest percentage of the waste. In practice it is generally preferable to have the tn angles it connected by a narrow marginal strip, such as shown at m.

On account of the difference in size between the triangle t and u the largest economy can consequently be effected by eliminating the waste of the triangles t. T 0 this end an L having a leg, whose end if square, is struck from the upper portion of a strip, whose width is 0;, so that corresponding squared ends of the legs of the L abut, as illustrated by the Us shown at l and l.

Where it is desirable to produce the Us l and 1 at the same stroke of the. punches, a Z-shaped punching would firsti result which would need to be subsequentlyi shearedinto the two US. This shearin coiil'd be done by a separate operation or y the provision cutting along the dividin line by means of a narrow blade either be ore or after the Z-punching was struck.

The best means, however, for practising this method atpresent known to me, accomplishes the production of the independent Us with one operation without the use of compound dies. This means comprises a punch, shown at P in Fig. 5, arranged for shearing the stock A along the irregular contour designated 6, f, g, h, i in Fig. 3.

When a punch having the shape indicated at P is reciprocated by the ram R of a punch press, as indicated in Fig. 4, each successive stroke of the ram would shear oft the Us separately, one abutting L. coming ofi' in ad Vance of the other, as will be readily understood by reference to Fig. 2.

In this figure, suppose the stock A has been fed into the punch press untiF it is' shorn along the line 6, f, g, it, i; then upon the upstroke of the ram the stock would be advanced a distance to give the desired width of the punching to be shorn ofl, so that upon the downward stroke of the ram the two independent [Us 4 and 4: would be produced.

After the next advance the punch would shear ofl the Us marked 5 and 5, then the Us marked 6 and 6 etc. in succession until the end of the stock is reached.

It is thus seen that the L-punching 5,

whose squared end abuts the homologous end of L-punching' 6, was stamped out one stroke in advance of the stroke which shears ofl the punching 6, but this is by no means the only contour that may be given to a punch which will shear off Ls from both sides of the stock in accordance with my invention, so that the Us on one side come off in advance of the other, since those on one sidev may be taken off any number of steps in1 advance of those shorn from the other sic e. Having now described an embodiment of my invention and the best method and means at present known to me for carrying the same into effect, I would have it understood that is merely for the purpose of illustration. Consequently I do not mean to be limited thereby to the exact details disclosed, nor in the choice of recognized equivalents in the practice of my invention except as defined in my claims hereunto annexed.

What I claim as new and desire to secure 4o of metallic stock of appreciably less than twice the width normally employed when punching shi gle rows of Ls, and in striking independent US from both sides of said, stock so that one pair of homologous legs abut,

2. The method of producing Lshaped punching which consists in taking a piece of metallic stock of appreciably less than twlce the width normally employed when punching single rows of Us, and in striking independent Ls from both sides of said stock so that the Us having abutting legs form a Z-punching.

3. The method of producing L-shaped punching which consists in takingxa piece of metallic stock of appreciably less the width normally employed when punching single rows of Ls. and -in striking -Ls from both sides of the stock so that one pair of homologous legs arbut permitting an independent L from one side to come oif in advance of that struck from the other side.

4. The method of producing interfitting uncomplementary laminated elements from stock sheet material with minimum waste, which consists in successively striking laminated elements from one side of the stock, and in simultaneouslystriking like elements han twice in abutting relations to the former from the other side of the stock from successive positlons where mdependent cutting operations may be performed.

my hand this 22nd day of October, 1918. JOHN J. FRANK.

In witness whereof I have hereunto set 

